As shown in FIG. 5, conventionally and generally, an A/D converter distributes an input voltage Vin by voltage divider DV1, compares the distributed voltage with an offset voltage using comparator array C, and converts the result of comparison into a digital signal having a predetermined bit width using encoder ED to provide an output D. The offset voltage is generated by reference voltage generating means, such as DV0.
In this way the conventional A/D converter has a rather large circuit and consumes a relatively large amount of electric power.